TV Eco sensor stopped working

UN55KU6300 TV with firmware 1231. Recently the eco sensor stopped working so the TV will no longer auto-dim even when the room is completely dark. At the same time the smart hub stopped working as well, but that was fixed with a smart hub reset. Disabling and re-enabling the eco sensor settings didn't help and even a factory reset of the TV didn't fix it.

The eco sensor stopped working once before but eventually fixed itself. Has anyone else ever encountered this issue?